[flang] Shifting function argument attributes to reflect type changes

[Renaud-K]

Summary

https://reviews.llvm.org/D137671 insured that when a function argument was inserted, argument attributes were properly shifted.
However, in the case the function body is empty, attributes are not shifted either.
This change addresses this by directly manipulating attributes for empty functions. Inserting arguments is not supported in this case, because they have no block arguments since they have no body.

[clementval]

LGTM

flang/lib/Optimizer/Transforms/AbstractResult.cpp

if (hasAbstractResult(funcTy)) {
           newArg = rewriter.create<fir::BoxAddrOp>(loc, bufferType, newArg);
         }
         patterns.insert<ReturnOpConversion>(context, newArg);
         target.addDynamicallyLegalOp<mlir::func::ReturnOp>(
             [](mlir::func::ReturnOp ret) { return ret.operands().empty(); });
         assert(func.getFunctionType() ==
                getNewFunctionType(funcTy, shouldBoxResult));
       } else {
+        llvm::SmallVector<mlir::DictionaryAttr> allArgs;
+        func.getAllArgAttrs(allArgs);
+        allArgs.insert(allArgs.begin(),
+                       mlir::DictionaryAttr::get(func->getContext()));
         func.setType(getNewFunctionType(funcTy, shouldBoxResult));
+        func.setAllArgAttrs(allArgs);
       }
     }
   }
 };
 
 inline static bool containsFunctionTypeWithAbstractResult(mlir::Type type) {
   return mlir::TypeSwitch<mlir::Type, bool>(type)
       .Case([](fir::BoxProcType boxProc) {

flang/test/Fir/abstract-result-2.fir

 // RUN: fir-opt %s --abstract-result-on-func-opt | FileCheck %s 
 
 // Check that the attributes are shifted along with their corresponding arguments
 
-//CHECK: func.func @_QMi8Pintrinsic_pack0(%arg0: !fir.ref<!fir.box<!fir.heap<!fir.array<?xi32>>>>, %arg1: !fir.box<!fir.array<?x?x?xi32>> {fir.bindc_name = "array"}, %arg2: !fir.ref<!fir.logical<4>> {fir.bindc_name = "mask"}, %arg3: !fir.box<!fir.array<?xi32>> {fir.bindc_name = "vector", fir.optional})
+// CHECK-LABEL: func.func @_QMi8Pintrinsic_pack0
+// CHECK-SAME:(%arg0: !fir.ref<!fir.box<!fir.heap<!fir.array<?xi32>>>>, %arg1: !fir.box<!fir.array<?x?x?xi32>> {fir.bindc_name = "array"}, %arg2: !fir.ref<!fir.logical<4>> {fir.bindc_name = "mask"}, %arg3: !fir.box<!fir.array<?xi32>> {fir.bindc_name = "vector", fir.optional})
 
 func.func @_QMi8Pintrinsic_pack0(%arg0: !fir.box<!fir.array<?x?x?xi32>> {fir.bindc_name = "array"}, %arg1: !fir.ref<!fir.logical<4>> {fir.bindc_name = "mask"}, %arg2: !fir.box<!fir.array<?xi32>> {fir.bindc_name = "vector", fir.optional}) -> !fir.box<!fir.heap<!fir.array<?xi32>>> {
   %0 = fir.alloca !fir.box<!fir.heap<!fir.array<?xi32>>>
   %1 = fir.alloca !fir.box<!fir.heap<!fir.array<?xi32>>> {bindc_name = "intrinsic_pack0", uniq_name = "_QMi8Fintrinsic_pack0Eintrinsic_pack0"}
   %2 = fir.zero_bits !fir.heap<!fir.array<?xi32>>
   %c0 = arith.constant 0 : index
   %3 = fir.shape %c0 : (index) -> !fir.shape<1>
   %4 = fir.embox %2(%3) : (!fir.heap<!fir.array<?xi32>>, !fir.shape<1>) -> !fir.box<!fir.heap<!fir.array<?xi32>>>
   fir.store %4 to %1 : !fir.ref<!fir.box<!fir.heap<!fir.array<?xi32>>>>
   %5 = fir.embox %arg1 : (!fir.ref<!fir.logical<4>>) -> !fir.box<!fir.logical<4>>
   %6 = fir.zero_bits !fir.heap<!fir.array<?xi32>>
   %7 = fir.embox %6(%3) : (!fir.heap<!fir.array<?xi32>>, !fir.shape<1>) -> !fir.box<!fir.heap<!fir.array<?xi32>>>
   fir.store %7 to %0 : !fir.ref<!fir.box<!fir.heap<!fir.array<?xi32>>>>
   %8 = fir.convert %0 : (!fir.ref<!fir.box<!fir.heap<!fir.array<?xi32>>>>) -> !fir.ref<!fir.box<none>>
   %9 = fir.convert %arg0 : (!fir.box<!fir.array<?x?x?xi32>>) -> !fir.box<none>
   %10 = fir.convert %5 : (!fir.box<!fir.logical<4>>) -> !fir.box<none>
   %11 = fir.convert %arg2 : (!fir.box<!fir.array<?xi32>>) -> !fir.box<none>
   %12 = fir.call @_FortranAPack(%8, %9, %10, %11) : (!fir.ref<!fir.box<none>>, !fir.box<none>, !fir.box<none>, !fir.box<none>) -> none
   %13 = fir.load %1 : !fir.ref<!fir.box<!fir.heap<!fir.array<?xi32>>>>
   return %13 : !fir.box<!fir.heap<!fir.array<?xi32>>>
 }
 func.func private @_FortranAPack(!fir.ref<!fir.box<none>>, !fir.box<none>, !fir.box<none>, !fir.box<none>) -> none attributes {fir.runtime}
+
+// CHECK-LABEL: func.func private @empty
+// CHECK-SAME:(!fir.ref<!fir.box<!fir.heap<!fir.array<?xi32>>>>, !fir.box<!fir.array<?x?x?xi32>> {fir.bindc_name = "array"}, !fir.ref<!fir.logical<4>> {fir.bindc_name = "mask"}, !fir.box<!fir.array<?xi32>> {fir.bindc_name = "vector", fir.optional})
+func.func private @empty(%arg0: !fir.box<!fir.array<?x?x?xi32>> {fir.bindc_name = "array"}, %arg1: !fir.ref<!fir.logical<4>> {fir.bindc_name = "mask"}, %arg2: !fir.box<!fir.array<?xi32>> {fir.bindc_name = "vector", fir.optional}) -> !fir.box<!fir.heap<!fir.array<?xi32>>>